Methods of and apparatus for operation of storage wells



METHODS OF AND APPARATUS FOR OPERATION OF STORAGE WELLS R.. D. HARVEY Filed Aug. 8, 1958 United States Patent 3,il8,433 METHGDS @F AND AIlARATEJS FGR @PERATEGN 0F STQRAGE WELLS Raymond D. Harvey, Hull, Ten, assignor, by mesne assignments, to Socony Mobil Gil (Iompany, Inc, New York, N.Y., a corporation of New York Filed Aug. 8, 1958, Ser. No. 754,697 6 Helms. (ill. 6T..5)

This invention relates to the storage of petroleum products in a storage well of the type formed in a salt formation and, more particularly, to methods of and apparatus for obtaining maximum storage of petroleum products in the storage well and has for an object the provision of simple and reliable methods of and apparatus for indicating when the storage limit of the storage well is being approached or has been attained.

In the art of storing petroleum products, usually liquefield petroleum gas, in storage wells formed in salt formations, concentric pipes are employed extending from the earth surface into a cavity formed in the salt formation.

The inner of the concentric pipes extends from the surface of the earth to a point near the bottom of the cavity while the outer of the concentric pipes extends from the surface of the earth to a point near the top of the cavity. The cavity is initially filled with brine or salt water which has been added to the cavity by way of the inner pipe. When it is desired to store the liquefied petroleum gas in the well, the product, in liquid form, is pumped into the well by way of the outer concentric pipe and under pressure to displace the brine or salt water which moves back to the surface by way of the inner pipe.

Because the storage well changes size with use due to the erosion or leaching effects of the salt Water, the capacity of the storage well increases. Therefore, it is dithcult to determine when the storage well has been filled to capacity with petroleum products without exhausting a considerable amount of product to the surface by way of the inner pipe. For example, one way of determining when the well has been filled is to add the liquefied petroleum gas until the salt Water-liquified petroleum gas interface has reached the bottom of the inner pipe. As soon as this occurs, the liquefied petroleum gas starts to exhaust from the well to the surface by way of the inner pipe and the exhausted gas may be observed at the surface. However, as much as 600 gallons to 800 gallons of liquefied petroleum gas can be exhausted in such a process. Such a large amount of waste has made prohibitive attempts to fill the well to full capacity.

In accordance with the present invention there is provided a method in which the liquid in the well adjacent the pipe is sampled in small amounts at a point removed from the large open lower end of the inner pipe. The samples are continuously carried to the surface with the brine and subjected to a detector. Upon detection of a sample containing liquefied petroleum gas, indicating that the liquefied petroleum gas-brine interface has reached the aforementioned point, the operator will have notice to shut down the input of petroleum product.

More particularly and in accordance with a preferred embodiment of the present invention, samples of the liquid adjacent the end of the center or inner pipe are brought to the surface with the brine; and these samples are exposed to a heated environment, preferably an open flame. The heated environment or open flame operates as a detector of the presence of liquefied petroleum gas in one or more of the samples by igniting the sample to produce a visual indication of the fact that the storage well is substantially filled to capacity.

Further, in accordance with the present invention, the inner pipe may be provided with a sampling port or aperture at a point adjacent to or remote from the open end in of the inner pipe. On the other hand, a separate small diameter pipe may be extended into the storage well to a point adjacent to the open end of the inner pipe and its upper end may extend to the earths surface for application of the samples to the detecting means for detection of the presence of the petroleum product.

For other objects and advantages of the present invention, reference may be had to the following written description and to the accompanying drawing which schematically illustrates a storage system embodying the present invention.

Referring now to the drawing, a storage well or cavity it) is illustrated as formed in a salt dome or formation 11 for the storage of petroleum products, such as, for example, liquefied petroleum gas; examples of which are propane and butane. The facilities associated with the storage well llil have been illustrated schematically to include a pair of concentric pipes 12 and 13. The pipe 12 extends from the surface of the earth and has its open end 14 in proximity to the bottom of the storage well or cavity 10. The outer concentric pipe 12 extends from the surface of the earth and has its open end 15 adjacent the top of the storage Well or cavity 19. In practice, the outer concentric pipe 12 provides a means for adding or withdrawing the liquefied petroleum gas to or from the cavity 1% While the inner concentric pipe 13 provides means for adding or withdrawing brine or salt water to or from the cavity 1%.

Assuming that the well if has been filled to capacity, that is, the interface 16, between the liquefied petroleum product 17 and the salt water 18 is at the dotted line position 16a just short of the open end 14 of the pipe 13, and that it is now decided to withdraw the product 17 from the well it], such withdrawal is performed by pumping water into the well by way of the pipe 13 to displace the product 17 from the well by way of the pipe 12. For this purpose, there is usually provided in the vicinity of the storage well a storage pit 19, the contents 20 of which, usually brine, are pumped by pump P and pass by way of pipe or conduit 13a and valve 22 from the storage pit 19 into the Well lit.

The addition of unsaturated salt water to the storage well causes aleaching action upon the salt walls of the well ill. As a result, the well becomes enlarged and its capacity is increased. Thus, it is now possible to store more product than previously in the same well. However, the extent of capacity increase is unknown. Should the operator attempt to fill the well to its new capacity, product invariably will be lost in the process and for the following reasons. The well will be filled to capacity when the salt water-product interface 16 reaches the position 16a adjacent the open end of pipe 13. Thereafter, additional product added by way of pipe 12 will escape to the surface by way of the pipe 13. Even if the escaping product is detected immediately, 600 to 800 gallons of product will be lost before the input to the well can be stopped. Accordingly, operators today hesitate to fill the wells to capacity and thus fail to take adrlllantage of the ever increasing storage capacity of the we In accordance with the present invention, there is provided method and apparatus for determining when the interface 16 has moved to a position just short of the open end 14 of the pipe 13 and makes possible the full use of well capacity. More particularly, samples of the liquid adjacent the lower end of the pipe 13 are withdrawn by way of one or more apertures 21 formed in the pipe 13. These samples are withdrawn from the well by way of the pipe 13 and thence by way of pipe 13a to a detector 36 which will indicate the presence of gas products in the samples.

The total area of the apertures 21 is made very small o with respect to the cross-sectional area of the pipe 13. Accordingly, the amount of gas which may be exhausted from the well during the process of detecting the arrival of the salt water-liquefied petroleum gas interface in the vicinity of the open end of pipe 13 will be very small. On the other hand, the pipe 13 may be made as large as necessary to permit rapid addition or withdrawal of salt water for eflicient operation of the storage facilities. Accordingly, the present invention provides a simple, inexpensive method for detecting filled condition of the storage well without interference with the proper operation of the facilities.

In a preferred embodiment, the detector comprises a heated environment as may be provided by one or more open flames 31 generated from nozzles 32 mounted atop a tank 33. When a sample withdrawn from the well by way of the apertures 21 includes some liquefied petroleum gas, the gaseous sample will bubble to the surface of the liquid in tank 33 and become ignited by the open flames 31 to indicate to the operator that the storage well is almost filled to capacity and that it is time to stop the inflow of liquefied petroleum gas to the well.

The tank 33 positioned within the storage pit 19 is provided with a series of ports 34 permitting liquid to enter or leave the tank from the storage pit 19. The pipe 13a has a portion 13b provided with ports 35 which serve as inlet or outlet means for the transfer of salt water between the well It) and the storage pit t9 and also serve as a means with the tank 33 for applying the samples to the vicinity of the flames 31.

In operation when a well is being filled with petroleum products, samples of the liquid adjacent the open end 14 of pipe 13 are withdrawn at a rate which is small compared to the rate of the liquid withdrawn by way of the open end 14. In other words, the volume of liquid per unit time withdrawn by way of the sampling ports 21 is small compared to the volume per unit time withdrawn by way of the very large open end of the pipe 13. The samples conducted by way of pipes 13 and 13a are emitted into the tank 33 and normally pass into the storage pit 19 by way of the ports 34. However, as soon as the interface 16 passes the ports 21, the samples will now include liquefied petroleum gas, which, under reduced pressure, is in a gaseous state and bubbles to the surface by way of ports and into the heated environment produced by the flames 31. A flare or flame will result with each sample containing gas and will notify an operator to close a valve, such as the valve 36, to stop the flow of petroleum products into the well 10.

Accordingly, the well can at all times be filled to capacity regardless of the size to which the walls of the well are enlarged by leaching processes and all without excessive loss of product. And such a method provides a simple, economical manner of operating storage wells at full capacity.

In accordance with a modification of the present invention, the sampling may be performed by extending a samplin tube 49 into the well by way of the pipe 12. The sampling tube has an open end 41 of diameter small compared with that of pipe 13 and terminates short of the open end 14 of the pipe 13. The opposite end of the sampling tube 46 is connected by way of valve 42 to the surface end of the pipe 13. Accordingly, when petroleum products are being added to the well it), samples of the liquid adjacent the open end 41 of the sam pling tube 49 continuously will be withdrawn from the well and applied to the detector 3t). When the interface 16 reaches the open end 41 of the sampling tube 40, the detector 30 will indicate by production of a gas flare or flame the location of the interface.

The inflammable material providing fuel to produce the flames 31 may be provided from a separate source of liquefied petroleum gas here indicated as a tank or reser voir 45 having an outlet connected to the jets 32 by way of conduit or pipe During operations there is a tendency for salts to deposit on the surfaces of the pipes extending into the well. The deposits are heavy enough eventually to clog the apertures 21 of pipe 13. In order to maintain the sampling system fully operative, the inside of the pipe 13 periodically may be washed with fresh water thus to dissolve the deposited salt. Such an arrangement is illustrated as including a pi 1e 5% extending from a source of fresh water (not shown) to a surface connection with the pipe 13. Whenever it is desired to wash out the pipe 13, valve 22 will be closed and valve 51 opened to permit flow of fresh water from the source and by way of pipe 5% and valve 51 to the pipe 13.

Likewise, when the pipe or tube 4%) is employed as a sampling tube, it will be desirable to provide a means for maintaining the aperture 41 free of salt deposits. Accordingly, he pipe connection 52 and the valve 53 may be provided for a flew of fresh water from a suitable source to the tubing 40.

Where the tube 40 with the aperture 41 is used, the operation of the well need not be suspended during the wash-out periods. Valves 22 and 36 respectively controlling the flow of salt water and petroleum product may remain open and the valve 53 may be opened to permit flow of resh water into the well by way of tube 49 without interference with the addition or removal of petroleum products from the well 10.

Now that the invention and one modification have been described, other modifications will become apparent to those skilled in the art all within the scope of the appended claims.

What is claimed is:

1. In a salt-cavity storage well for liquids of the type in which liquid petroleum products are added under pressure at the top of the cavity and displace a liquid solution of brine by way of an open-ended pipe extending from a point near the bottom of the storage well to a point at the surface of the earth, the method of filling the storage well to capacity with the liquid petroleum product comprising the steps of adding the liquid petroleum product to the storage well, with the addition of the liquid petroleum product removing by way of the aforementioned pipe the liquid solution of brine for disposition at the surface of the earth, continuously withdrawing samples of the liquid from a point above the open end of the pipe at a flow rate small compared with the flow rate with which the volume of the solution of brine is being withdrawn by the pipe, detecting for the presence of petroleum product in the samples, and upon the detection of petroleum product in the samples, stopping the addition of the liquid petroleum product to the storage well.

2. The method of claim 1 in which the presence of the petroleum products in the samples is detected by exhausting the samples to the atmosphere in the vicinity of an open flame.

3. In a salt-cavity storage well system, the combination which comprises a cavity having an inlet through which liquid petroleum product is added under pressure to fill said cavity, an open-ended conduit extending from a point near the bottom of the cavity to a point at the surface of the earth through which a liquid solution of brine is displaced from the cavity upon the addition of said liquid petroleum product to said cavity, sampling means in close proximity to and at a point above the open end of said conduit near the bottom of said cavity and leading to the interior of said conduit for withdrawing samples of the liquid in the cavity into said conduit at a flow rate small compared with the flow rate at which the volume of said solution of brine is withdrawn from said cavity by said open-ended conduit, a valve for controlling the flow of said liquid petroleum product into said inlet, and a petroleum product detector cou led to the other end of said conduit at the surface of the earth for detecting the presence of petroleum product flowing through said conduit whereby said valve may be closed to step the addition of said liquid petroleum product to said cavity before the interface of the petroleum product and said solution of brine reaches said open end of said conduit near the bottom of said cavity.

4. The system of claim 3 in which said sampling means comprises at least one aperture extending through the wall of said conduit at a point in close proximity to and above the open end of said conduit and in which the cross-sectional area of said aperture is very small compared with the cross-sectional area of the open end of said conduit.

5. The system of claim 3 in which said sampling means comprises a sampling tube connected with the interior of said conduit intermediate the ends thereof and having an opening in close proximity to and at a point above the open end of said conduit near the bottom of said cavity, said opening having a cross-sectional area very small compared with the cross-sectional area of the open end of said conduit.

6. In a salt-cavity storage well system, the combination which comprises a cavity having an inlet through which liquid petroleum product is added under pressure to fill said cavity, an open-ended conduit extending from a point near the bottom of the cavity to a point at the surface of the earth through which a liquid solution of brine is displaced from the cavity upon the addition of said liquid petroleum product to said cavity, a storage means located at the surface of the earth, a vessel mounted in said storage means and having secured at the top thereof flame producing means, said conduit terminating in said vessel for transfer of said solution between said cavity and said storage means by way of said conduit, means in close proximity to and at a point above the open end of said conduit near the bottom of the cavity for continuously withdrawing samples of the liquid in the cavity at a flow rate small compared with the flow rate at which the volume of said solution of brine is withdrawn from said cavity by said open-ended conduit, said means including at least a portion of said conduit for transmitting said samples to said vessel for exposure to said flame producing means during the addition of said liquid petroleum product to the well for the detection of the presence of petroleum product in the samples and the indication of the arrival of the interface of the petroleum product and said solution of brine at said point adjacent the open end of said conduit, and a valve for stopping the flow of said liquid petroleum product to said inlet and thereby to said cavity before the interface of the petroleum product and said solution of brine reaches the open end of said conduit near the bottom of said cavity.

References Cited in the file of this patent UNITED STATES PATENTS 1,008,830 Lamb Nov. 14, 1911 1,906,834 Beckwith May 2, 1933 2,627,745 Matteson Feb. 10, 1953 2,659,209 Phelps Nov. 17, 1953 2,713,775 Cottle July 26, 1955 2,752,776 Kaplf July 3, 1956 2,772,564 Dougherty Dec. 4, 1956 2,787,125 Benz Apr. 2, 1957 2,869,328 Gibson Jan. 20, 1959 2,880,593 Johnson Apr. 7, 1959v 2,928,247 Hubbell Mar. 15, 1960 2,938,383 Blackburn May 31, 1960 FOREIGN PATENTS 612,818 Canada Jan. 17, 1961 

1. IN A SALT-CAVITY STORAGE WELL FOR LIQUIDS OF THE TYPE IN WHICH LIQUD PETROLEUM PRODUCTS ARE ADDED UNDER PRESSURE AT THE TOP OF THE CAVITY AND DISPLACE A LIQUID SOLUTION OF BRINE BY WAY OF AN OPEN-ENDED PIPE EXTENDING FROM A POINT NEAR THE BOTTOM OF THE STORAGE WELL TO A POINT AT THE SURFACE OF THE EARTH, THE METHOD OF FILLING THE 